Background: In Morocco, Kidney cancer is the 18th most common tumour and the 19th lethal cancer in 2020. The average age of diagnosis is 65 years and men are more affected. Molecular studies of renal cell carcinoma (RCC) allowed the detection of several genetic abnormalities in each histological subtype. These aberrations got different diagnostic value depending on their specificity, prognostic implication and for some a therapeutic utility since the development of targeted therapies. The aim of our study is to evaluate the utility of fluorescence in-situ hybridization (FISH) in the diagnostic and the prognostic categorization of patients with renal cell carcinoma. Methods: We included prospectively cases of RCC diagnosed after histological examination and immunohistochemistry analysis for some cases. The methodology consisted in highlighting by FISH molecular abnormalities for each histological subtypes using Zytolight probes. Probes were chosen depending on the histological diagnosis and their corresponding molecular abnormalities. Results: A total of 30 cases of RCC were included. Clear cell carcinoma (ccRCC) represented 56,6%(17 cases) followed by papillary RCC (pRCC) with 20% (6 cases), chromophobe RCC (chRCC) with 10% (3 cases), 2 cases (6,6%) with uncertain diagnosis clear cell carcinoma or papillary carcinoma and one case of renal oncocytoma (RO) (3,3%), tubulo-cystic RCC tcRCC (3,3%). The FISH method supported the morphological diagnosis in all cases except in one biopsy diagnosed histologically as a ccRCC and this method allowed the diagnosis correction to a pRCC by the detection of a polysomy of chromosome 17 described in this histological subtype. The FISH method can also be used in prognostic categorisation of patients by the detection of some genetic aberrations with a prognostic implication like the loss of CDKN2a located in the long arm of chromosome 9 which predict a worse diagnosis. Conclusions: FISH method got an good performance in the diagnostic approach of RCC especially in cases with non-conclusive histology and immunohistochemistry. It can also be used in the prognosis of this tumour in addition to other histo-prognostic factors. This method will lead to more precision in diagnosis and better care management personalisation in RCC.